Hydroacoustic apparatus



Dec. 1963 J. v. BOUYOUCOS 3,

HYDROAGOUSTI C APPARATUS Filed Feb. 10, 1967 2 Sheets-Sheet l I INVENTOR.

JOHN M souroucos BY H/ ATTORNEY Dec. 10, 1968 J. v. BOUYOUCOS HYDROACOUSTIC APPARATUS 2 Sheets-Sheet 2 Filed Feb. l0, 1967 INVENTOR. JOHN M BOUYOUCOS HIS A 7' TORNE Y United States Patent 3,415,330 HYDROACOUSTIC APPARATUS John V. Bouyoucos, Rochester, N.Y., assignor to General Dynamics Corporation, a corporation of Delaware Filed Feb. 10, 1967, Ser. No. 615,090 16 Claims. (Cl. 175--56) ABSTRACT OF THE DISCLOSURE A hydroacoustic drilling apparatus is described. The apparatus modulates a column of liquid acted upon by a self-excited valving member which is resiliently and yieldingly urged to a center position by a mechanical spring in the apparatus. A driven rotating drill string, coacting with the modulating fluid column penetrates the earth formation while fluid jets urge chips and cuttings up the bore hole. Modulation of the fluid is substantially confined to the bottom of the bore hole by filter elements on the driven drill string.

The invention relates to hydroacoustic apparatus, and more particularly to a method and apparatus for drilling and boring holes in the earth formation.

The invention is especially suitable for use in oil well drilling and other apparatus where deep bore holes are drilled into the earth formation with the assistance of drilling fluids.

When drilling to great depths in the earth formation, steady state or DC fluid pressures acting upon the bottom of the bit cavity tend to hold down chips broken off the earth formation by the drill bit. This action results in relatively low drilling speeds and increases high drill bit wear. This problem of low drill speed, bit wear and low efiiciency is of long standing in the field of oil well drilling and elsewhere where deep bore holes are required.

Accordingly, it is an object of the present invention to provide an improved method and apparatus for drilling or boring holes.

It is yet another object of the present invention to provide an improved method and apparatus for drilling or boring holes in an earth formation, especially at great depths.

It is a further object of the present invention to provide improved methods and apparatus for facilitating the removal of chips, cuttings and the like from the bottom of deep bit cavities in the earth formation.

It is a still further object of the present invention to provide an improved apparatus for modulating a fluid pressure in the bottom of a bore hole or bit cavity and for substantially isolating the pressure variations within the bit cavity.

It is a still further object of the present invention to provide an improved hydroacoustic apparatus especially suitable for use in drilling and boring tools.

It is a still further object of the present invention to provide improved acoustic vibration generating apparatus which efiiciently operate with drilling fluids, such as muds.

Another object of the present invention is to provide improved apparatus for boring holes in the earth formation which will not enlarge, cavitate or damage the side walls of bored holes in the earth formation.

Briefly described, the apparatus includes an acoustic generator and a mechanical drilling bit which coact to drill or bore a hole in the earth formations with the use of drilling fluid. The acoustic generator modulates the pressure in the bore hole region adjacent to the drill bit, called the bit cavity herein, and further provides jets of fluid which facilitate the removal of chips and other debris from the bit cavity. Embodied within the acoustic generator is a valving member movable in a porting region between a center first position and a fluid flow throttling second position. The valving; member is urged to the center position by a mechanical spring so configured and arranged to provide one or more of the following advantages:

(1) Eliminates the need for hydraulic centering circuits which is particularly important when the fluid is a drilling mud.

(2) Permits a non-metering end of the movable valve member to efliciently act as a piston on a column of liquid (viz a transmission line) for a generating acoustic energy ivhich is coupled to the bottom of a bored hole or oad.

(3) Permits the porting region to be contoured, in a desired manner, to provide for a desired flow regulation.

An important feature of the present invention is the provision of means for isolating or confining the pressure fluctuations within the bit cavity to prevent damage to the side walls of the bored hole in a return path of the mud carrying the chip and cuttings from the bit cavity.

Another important feature of the invention resides in configuring the valve, isolating means, and the jets and drill bit to permit effective power transmission from the oscillating valving member to the bit cavity, with a maximum transfer of power or energy.

The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof will become more readily apparent from a reading of the following description in connection With the accompanying drawings in which:

FIG. 1 is a diagrammatic sectional view showing a hydroacoustic apparatus in accordance with one embodiment of the invention;

FIG. 2 is a cross-sectional view taken along the lines 22 of FIG. 1;

FIG. 3 is a schematic diagram of an acoustic circuit of the apparatus shown in FIG. 1;

FIG. 4 is a diagrammatic sectional view showing a by droacoustic apparatus in accordance with another embodiment of the invention;

FIG. 5 is a cross-sectional view taken along the lines 55 of FIG. 4; and

FIGS. 6 and 7 are fragmentary sectional views showing stator port and valve arrangements in accordance with the invention.

The present invention may be embodied Within a number of different varieties of drilling tools. One such type may be used in the oil well drilling art which includes a rotatable bit head, a rotating table driven by a driving motor for rotating the bit head, a mud pump, and all the other standard equipment known to the art.

Turning now to FIGS. 1 and 2, a drill bit 10, having three rotably mounted conically shaped drilling members 11, each spaced about from the other is shown in the bit cavity 12. Such types of drill bits (often referred to as a Y bit) are well known in the art (see for example those shown in catalog No. 66 (1966) published by the Reed Roller Bit Company of Houston, Tex U.S.A.). As the drill bit 10 is rotated, it penetrates deeper and deeper into the earth formation.

The mechanical efficiency of the drilling operation has been found to progressively decrease as the drill bit penetrates into the earth formation. It has further been found that by modulating the pressure in the bit cavity 12 (viz. the excavated bore hole region adjacent the drill bit 10), the mechanical efficiency of the drilling operation may be greatly increased. Moreover, it has also been found that it is important to isolate the pressure fluctuations within the bit cavity 12 to prevent damage to the side walls in an annular return path 13 of the bore hole, defined between the tool and the earths formation Drilling mud carrying the cuttings from the bit cavity 12 is recirculated back up to a mud pump, not shown.

A hydroacoustic drilling tool incorporating the invention is shown in FIG. 1 and includes a cylindrical drill string 34 connected to an acoustic vibration generator 36, having a housing 15. The drill string 34 and the generator 36 may be cylindrical in shape. The drill string 34 includes an axial bore 37 communicating between a cylindrical cavity 39 in the generator 36 and the mud (no-t shown). In order to simplify the drawing and to show the structure of the apparatus, the drilling mud has not been shown in the apparatus and the bore hole. In addition, although a screw connection 38 is shown between the drill string 34 and the housing of the generator 36, it should be understood that other types of fasteners may be provided to connect these two sections.

Leading downwardly from the cavity 39 is an annular path 42 which opens into an active cavity 44, of substantially cylindrical configuration. Preferably, the length of the channel 42 should be approximately one-quarter of a wave length (at the operating frequency) so that the channel 42 will be viewed as a high impedance, as seen by the active cavity 44. It will be noted that the active cavity 44 has a lower surface 46 which is conically shaped, for reducing turbulence in the flow path. By active cavity is meant that the cavity supports dynamic (A.C.) pressure variation at the frequency of oscillation of the apparatus.

From the active cavity 44, the fluid or drilling mud passes by a metering edge of orifice 50 and a stator port 52 out into a cylindrical discharge cavity 56. From the cavity 56, fluid flows through a series of radially disposed ports 58 through the housing 15 of the generator'36 into a return annulus 13 defined by drill string 34, the generator 36 and the earths formation. In the annulus 13 the fluid combines with the flow of the drilling mud from the bit cavity 12 and passes up into the input section of the mud pump. It is desirable to have the return flow of the mud or the fluid to the mud pump in a steady state or a DC flow; in other words, the fluid flow should be characterized by an absence of fluid pressure or modulation fluctuations. The structure for accomplishing this function will be discussed hereinafter.

The acoustic generator 36 includes a valve partially disposed in the cavity 56 and coaxially aligned and guided by a journal bearing 64. The valve 62, longitudinally reciprocates in the cavity 56 in a manner so that its top surface is movable into and out of the stator port 52, closing and opening the orifice defined by the metering edge 50, thereby modulating an otherwise steady flow of fluid. The lower or piston portion of the piston 62 is disposed within a transmission line 66 which couples the modulated fluid pressure to the bit cavity 12.

The valve 62 moves back and forth between its open and closed positions about a center position in the stator port 52 in a self-excited mode in response to the circulation of the drilling mud. The lower piston portion of the valve '62 operates on the transmission line 66 to transmit acoustical vibrations down into the bit cavity 12.

Coupled to the top surface of the valve 62 is an elongated cylindrical member 70 of resilient material which provides a mechanical spring function. More specifically, the spring 70 extends in coaxial relationship through the cavity 44 and the bore hole 42 up into the cavity 39 where it is fastened by means of a series of bolts 78 to the housing 12. The diameter of the hole 42 is greater than that of the spring, thereby providing an annular flow path. Holes '79 are provided in the top portion of the spring 70 to permit mud to flow from the cavity 39 to the hole 42. By means of this arrangement, the spring member will not interfere with the flow pattern of the drilling mud. It should be mentioned that the mechanical termination for the spring 70 does not necessarily have to be placed within the cavity 39, but could be dis- 4 posed either above or below the valve 62 as shown in FIG. 4.

Inasmuch as the average pressure on the upper surface of the valve 62 is greater than the average pressure on the return side of the valve, there is a static force on the valve 62 which is proportional to the net difference between the supply and return pressures and which creates a static elongation of the mechanical spring member 70, placing the spring member under tension which permits it to better be able to resist buckling.

For more efficient operation of the generator 36, the average or center position of the valve member 62 during oscillation should be in line with the metering edge 50 or within the stator port 52 (viz. Class Copen during less than half a cycle-0perati0n). In the absence of supply pressure, the edge of the valve 62 would thus be within the stator port 52. However, as the supplied pressure increases, the valve would move downwardly until its edge is approximately in line with the metering edge 52. At this point, oscillations commence and reach a full amplitude. A reduction in the supply pressure causes the average position of the top surface of the valve to be slightly above the edge 52, thus providing Class C operation.

It is to be noted that the valve '62 is terminated or acted upon on both its end surfaces by fluid columns that provide reflection feedback upon the valve 62 to support selfsustained oscillations. It is an important feature of the invention that the valve is centered by the mechanical spring member 70 whose stiffness controls the static or average valve position and also affects the oscillators resonant frequency.

The transmission line 66 actually branches from a single coaxial line 66a into two channels 66b and 660 aligned with respect to the center line of the drilling tool, so as to form a Y shaped transmission line 66. When the valve 62 oscillates, the lower end of the valve 62, by way of the transmission line 66, modulates the pressure in the bit cavity 12. The mud is returned to the earths surface pump by the annular return channel 13 between the earth formation and the outer periphery of the generator 36 and the drill string.

The center line path from the bore hole along either the channel path 66a and 661) or 66a and 660 has been dimensioned to be substantially one-quarter of a wave length at the operating frequency. This is an important consideration which will be seen when the equivalent acoustical circuit of FIG. 3 is described. Suflice it here to say, however, the role of the transmission line 66 is to transform the relatively high impedance of the load to a suitable low load impedance, as seen by the valve 62, to effect proper impedance matching, thereby permitting the valve 62 to oscillate with suflicient amplitude.

In order to prevent appreciable transmission of vibratory energy along the mud return channel 13 and thereby isolate or confine pressure fluctuations Within the bit cavity 12, an acoustic termination has been provided, less than a one-quarter wave length at the oscillation frequency, up from the bottom of the bit cavity 12. As shown, the acoustic termination is provided a compliant member 80 which retains its compliance in spite of the high hydrostatic pressures found in its vicinity. The member 80 comprises a hollow cylinder having a flexible outer wall and which is filled with pressurized gas, say for example nitrogen. The role of the member 80 will again be discussed with reference to the acoustic circuit discussed later in this specification.

Four jet channels provide communication between the cavity 44 and the bit cavity 12 and are adapted to force jets of high pressure mud into the bit cavity 12, thereby providing the needed fluid flow for cleansing action for the drill bits and removal of the cuttings from the bit cavity 12. A gas desurger 106 for each line 100 is spaced in the flow path about one-quarter wave length from the cavity 44. With this arrangement, each desurger 106 is viewed by the bit cavity 12 to be a pressure source, and so that when the pressure is reduced in the bit cavity 12, the desurger 106 will cause high velocity jet streams to be injected into the bit cavity 12, whereas when the modulation pressure increases, the flow from the jets will be retarded. By way of illustration only, an example of a desurger which may be used in the practice of this invention may be a gas-filled rubber bag confined within a cavity (similar to member 80). Conduits communicate the fluid pressure in the lines 100 to the bag.

Referring to FIG. 3, there is shown an equivalent acoustic circuit for the apparatus of FIG. 1. The source 122 represents the oscillating pressure of the mud estabished by the rear portion of the piston 62 which operates on the transmission line 66. The transmission line 66 is shown effectively to be a transformer, the secondary winding of which is connected to the bit cavity compliance (C paralleled by the inertance L of the annular discharge path between the tool and the earth formation and which extends from the bottom hole cavity 12 up to the terminating compliance 80. Further paralleling (C and (L) is the resistance (R provided by the jet channels 100 which in fact constitute the major load on the oscillator.

By selectively choosing and sizing the various acoustic values, the circuit may be made to be antiresonant so that the valve 62 effectively sees or is coupled to only the jet channel resistance R thereby providing maximum power transmission and isolation of the pressure modulation within the bit cavity 12.

In operation, flow from the mud pump is delivered to the cavity 39 and then passes along the annular path 42 until it enters the active cavity 44 of the tool. As noted above, the annular feed path 42 should be approximately one-quarter of the wave length in dimension so that the cavity 39 is viewed by the active cavity 44 as having high impedance. From the active cavity 44, the fluid passes by the metering edge 50' of the stator port 52 into the discharge cavity 56 and then out through the side ports 58 into the return annulus 13 between the tool and the earths formation. As a result of this fluid flow, the valve 62 oscillates in a self-excited manner and causes the transmission line 66 to couple energy from the valve 62 to the bit cavity 12, thereby modulating pressure in that region. The pressure modulation is effectively isolated within the bit cavity 12 by means of the compliant members 80 which tunes the resonant acoustical circuit in the manner just previously described.

Referring to FIGS. 4 and 5, the parts corresponding in function to those described with the FIG. 1 apparatus, primed numbers will be used to designate the corresponding elements. As shown, the valve member 110 is disposed in the discharge cavity 56' and is adapted to move into out of flow throttling relationship with the stator port 52. The valve 110 is formed at the free end of a member 112, which is actually hollow, providing the coaxial portion 66a of the transmission line 66', and which extends downwardly, merging into two Y shaped channels 66b and 66c. As with the previous arrangement, the transmission line 66' is dimensioned to be one-quarter wave length at the operating frequency. In forming this internal cavity, the elongated member 112, which defined the cavity, plays the role of a mechanical spring.

Acoustic energy will be extracted from the cavity 66' as the valve oscillates in a self-excited mode and transmitted down to the bit cavity 12'. In other Words, the cross-sectional area forming the transmission line 66 will be varied as the valve 110 oscillates, and thus, acoustic energy will be coupled from the valve 110 into the bit cavity 12'.

The equivalent acoustic circuit for this embodiment is also shown by FIG. 3.

In accordance with the invention, it has been found that by shaping the stator port and the front end of the valve member, static flow characteristics of the valve may be changed and a desired flow regulation may be achieved.

In FIG. 6, the free end surface 132 of a valve member 134 is shown to be hernisp-herically shaped and is adapted to cooperate with a metering edge 136 and an arcuate surface 138 which flares downwardly and outwardly from the metering edge 136. This configuration has an advantage in that it permits a greater ease of self-starting.

In the stator port 140, shown in FIG. 7, the free end of the valve 141 is formed by a planar surface 142 (perpendicular to the center line C/ L of the apparatus 36) and which merges into a flaring downwardly and outwardly frustroconical surface 144. The surface 144, is adapted to cooperate with a metering edge 146 and] a frustro-conical surface 148 which flares downwardly and outwardly from the metering edge 146 into the return cavity 56 (see FIG. 1). By varying the illustrated angles 0 and 6 etfective control over the flow rate and power capacity of the oscillator may be achieved.

If the displacement of the valve (pulse amplitude) members 131 or 141 is larger than the strength of the chamfer or flared portion of the porting structure, the mode of operation approximates Class C operation with limited flow when the pressure drop across the orifice is high and substantially increases flow capacity at the opened end of the stroke when the pressure dropacross the orifice is low. This leads to increased power conversion efliciency. In the case of FIG. 2 where the full amplitude is larger than the length of the flared or chamfered portion, oscillation can commence in a Class B mode and open to full ampulitude under Class C conditions.

For ease of self-starting, a discontinuity in slope is preferred at the metering edges. Beyond this, however, the shape of the edges can be programmed to achieve a desired static characteristic flow curve, or family of curves. Thus, for example, a general shape might differ somewhat from the spherical as shown in FIG. 6.

It will be appreciated that variations and modifications of the herein described illustrative embodiments of the invention will be apparent to those skilled in the art and should be taken merely as illustrative and not in a limiting sense.

What is claimed is:

1. Apparatus for drilling a hole in an earths formation with the aid of a, source of pressurized fluid and a drill bit disposed in a bit cavity at the bottom of said hole, said apparatus comprising an acoustic-vibration generator coupled to said source for delivering fluid to and substantially modulating the pressure of the fluid at said bit cavity to increase the drilling efficiency of said apparatus, said acoustic-vibration generator comprising:

(a) a housing having passage means for conducting a flow of fluid from said source through said generator to said bit cavity, said passage means comprising an active cavity, a stator port, a discharge chamber and ports in said housing leading to a discharge annulus between said apparatus and said earth formation at the side of said bit cavity,

(b) a valve mechanism including a mechanical spring supported by said housing and a valve fixed to said spring so as to be disposed adjacent to said stator port and adapted to move in relation to said port between an open first position and a fluid flow throttling second position, and

(c) said passage means and said valve mechanism being contoured in relation to said hole to define an acoustic circuit for supporting self-exciting oscillatory movement of said valve at an operating frequency thereby moving said valve between said positions, and producing pressure fluctuations in said bit cavity.

2. The invention as set forth in claim 1 wherein said passage means includes a channel coupling said pressurized fluid source to said bit cavity for supplying a jet of said fluid to said bit cavity.

3. The invention as set forth in claim 1 wherein said active cavity is coupled to said source and wherein said spring and said valve are integral with each other to define an elongated flexible member contoured to define a hollow cavity in communication with said bit cavity, fixedly secured to said housing and terminating in a top free end forming said valve.

4. The invention as set forth in claim 3 wherein said hollow cavity is dimensioned to be substantially one-quarter of a wavelength at said operating frequency.

5. The invention as set forth in claim 1 wherein said passage means includes a transmission line coupled to said bit cavity, said cavity having a piston portion which reciprocally moves in a path within said transmission line to modulate the pressure in said bit cavity.

6. The invention as set forth in claim 5 wherein said transmission line has a length substantially equal to onequarter of awavelength at said operating frequency.

7. The invention as set forth in claim 5 wherein said passage means includes a jet channel coupling said active cavity to said bit cavity for supplying a jet of fluid to said bit cavity.

8. The invention as set forth in claim 7 including isolation means disposed in said housing in said discharge annulus for tuning said acoustic circuit so that said valve sees substantially only the resistance provided by said jet channel.

9. The invention as set forth in claim 1 wherein said spring is an elongated member fixed to said housing above said valve member coaxially aligned in relation to the flow path through said apparatus and thereby tensioned by said pressurized fluid.

10. Apparatus for drilling a hole in an earths formation with the aid of a source of pressurized fluid and a rotatable drill bit disposed in a bit cavity at the bottom of said hole, said apparatus comprising an acoustic-vibration generator coupled to said source for delivering fluid to and substantially modulating the pressure of the fluid at said bit cavity to increase the drilling efficiency of said apparatus, said acoustic-vibration generator comprising;

(a) a housing having passage means for conducting a flow of fluid from said source through said generator to said bit cavity, said passage means being contoured to define a stator port,

(b) a valve mechanism including a mechanical spring supported by said housing and a valve member fixed to said spring and disposed adjacent said stator port and adapted to move in relation to said port between an open first position and a fluid flow throttling second position for modulating the pressure within said bit cavity,

(0) isolation means for confining the pressure modulations within said bit cavity, and

(d) said passage means and said valve mechanism and said isolation means being disposed to define a T680- nant acoustic circuit for supporting self-exciting oscillatory movement of said valve, thereby moving said valve between said positions, thereby producing pressure fluctuations in said bit cavity.

11. The invention as set forth in claim 10 wherein said passage means includes a one-quarter wavelength transmission line coupled to said bit cavity, said valve having a piston portion which reciprocally moves in a path within said transmission line to modulate the pressure in said bit cavity.

12. The invention as set forth in claim 11 wherein said passage means includes a jet channel coupling said active cavity to said bit cavity for supplying a jet of liquid to said bore hole and wherein said housing is provided with a compliant member opening onto said cavity about onequarter of a wavelength of the operating frequency from Where said channel opens into said active cavity.

13. The invention as set forth in claim 12 wherein said compliant member is a gas bag.

14. Apparatus for drilling a hole in an earths formation with the aid of a source of pressurized fluid and a drill bit disposed in a bit cavity at the bottom of said hole, said apparatus comprising an acoustic-vibration generator coupled to said source for delivering fluid to and substantially modulating the pressure of the fluid at said bit cavity to increase the drilling efficiency of said apparatus, said acoustic-vibration generator comprising:

(a) a housing having passage means for conducting a flow of fluid from said source through said generator to said bit cavity, said passage means being contoured to define a stator port,

(b) a valve mechanism supported by said housing and a valve member disposed adjacent said stator port and adapted to move in relation to said port between an open first position and a fluid flow throttling second position for modulating the pressure in the bore hole,

(c) isolation means for confining the pressure modulations within said bore hole region,

(d) said passage means and said valve mechanism and said isolation means being disposed to define a resonant acoustic circuit for supporting self-exciting oscillatory movement of said valve moving it between said positions, thereby producing pressure fluctuations in said bore hole, and

(e) said passage means including a jet channel coupling said active cavity to said bit cavity for supplying a jet of liquid to said bore hole and wherein said housing is provided with a compliant member opening onto said cavity about one-quarter of a Wavelength of the operating frequency from where said channel opens into said active cavity.

15. The invention as set forth in claim 14 wherein said compliant member is a gas bag.

16. The invention as set forth in claim 15 wherein said passage 'means includes a one-quarter wavelength transmission line coupled to said bit cavity, said valve having a piston portion which reciprocally moves in a path within said transmission line to modulate the pressure in said bit cavity.

References Cited UNITED STATES PATENTS 2,713,472 7/1955 Bodine -56 2,982,255 5/1961 Klenck 17556 X 3,018,834 1/1962 Cook 17592 3,094,176 6/1963 Cook 17592 3,163,240 12/1964 Bodine 17556 3,346,058 10/1967 Bouyoucos 17556 3,371,726 3/1968 Bouyoucos 17556 X NILE C. BYERS, 111., Primary Examiner. 

